Mosquito control oil promoted with polyethoxylated 2,4-dinonyl phenol and method of using it



- March 10, 1970 s. v., CHAMBERS 3,499,969

MOSQUITO CONTROL OIL PROMOTED WITH POLYETHOXYLATED 2,4'DINONYL PHENOL AND METHOD OF USING IT Filed July 17. 1967 INTERFACIAL TENSIDN E (8) DNP IN 500-600F. PARAFFINIC OIL WT. H8) DNP 'wo/sam NOISNHI'IVIOVJHBINI INVENTOR. GILBERT V- CHAMBERS,

United States Patent US. Cl. 424-341 25 Claims ABSTRACT OF THE DISCLOSURE The effectiveness of mosquito control oils is enhanced by the inclusion of at least about 0.2 weight percent (and up to an upper limit of about 3.75 weight percent) of a promoter, ethoxylated 2,4-dinonyl phenol, wherein the ethoxylated substituent contains from about 6 to about 14 ethoxy units.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 604,790, filed Dec. 27, 1966, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention pertains to the killing of aquatic stages of insects by application of an oily material to the surface of the aquatic breeding grounds of the insect.

Description of the prior art The prior art has utilized hydrocarbon oils such as diesel fuel as a surface-applied insecticide for killing aquatic stages of insect life. However, it has been necessary to use about 20 gallons per acre as a treat rate. In an attempt to avoid the high cost of application with such a high application rate of the diesel fuel, chemical insecticides have been used instead of diesel fuel. However, this is also expensive and has not been particularly effective due to the rapid development of resistant strains in the mosquito population. Addition of surfactants also has been tried, but the effect of the surfactant has merely been that the oil has spread more evenly across the pond surface, thereby increasing the chance that the mosquito, larvae and pupae would come in contact with the oil. The effectiveness of the oil as a toxic material per se has not been affected.

SUMMARY OF THE INVENTION The present invention relates to a promoted oil having toxicity towards the aquatic stages of insect life, particularly the larvae and pupae of mosquitoes. More particularly, the present invention relates to a novel mixture of materials whereby an oil, having a toxicity towards mosquito larvae and pupae, is enhanced manyfold in its toxicity and effectiveness, allowing the use of much smaller treat rates when applying the oil to the surface of breeding ponds. In its most specific aspect, the present invention relates to a mixture of a mosquito oil with a promoter, ethoxylated 2,4-dinonyl phenol, which is used in effective amounts of at least 0.2 weight percent of the mixture, and a method of using this promoted mixture in the control of mosquito proliferation.

BRIEF DESCRIPTION OF THE DRAWING The sole figure is a graph showing the relationship between interfacial tension and the quantity of ethoxylated 2,4-dinonyl phenol in a 500-600 F. paraflinic oil.

3,499,969 Patented Mar. 10, 1970 ice DESCRIPTION OF THE PREFERRED EMBODIMENTS Mosquitoes are well known as carriers of such pathogens as the encephalitis virus and malaria bacteria. It is essential in preventingdiseases caused by such pathogens to control the proliferation of the mosquito carriers of the pathogen. This can best be accomplished by breaking the mosquito life cycle rather than by attacking the adult mosquito itself.

The mosquito in its life cycle passed through three stages before obtaining maturity: egg, larva, and pupa. The most effective way of controlling mosquito proliferation is by breaking the life cycle; i.e., by attacking the proliferating mosquitoes before they reach maturity. Since the early stages of mosquito development are aquatic, the means chosen to break the life cycle must be adapted to kill the immature mosquito while it is in the water.

Heretofore the use of oils for covering the surface of mosquito breeding ponds has not been too effective unless used in high concentrations. For example, No. 2 diesel oil is applied in amounts ranging from 20 to 40 gallons per acre of surface. This is uneconomical. The present invention provides promoted oil which, by use of a very small amount of a relatively cheap material, enhances manyfold the toxicity of the oil itself, and the mixture can be used effectively in amounts as low as one gallon per acre of water surface.

The present invention, although encompassing the admixture of the promoter with diesel oil, is most valuable in allowing the use of more expensive and more effective oils for mosquito control, rather than the diesel fuel. Further, since the amount of oil that is to be applied can be reduced to a very small level, the use of the cheaper diesel fuel can be enhanced in its effectiveness.

The present invention involves the use of ethoxylated 2,4-dinonyl phenol as a promoter for oils which already have a toxicity toward the aquatic stages of mosquito life. The ethoxylated 2,4-dinonyl phenol is not itself toxic toward mosquito life and does not render toxic those oils which are not in themselves toxic (for example, heavy paraifinic oils boiling above about 750 F.). The precise role of the promoter is not known, but by inspection of the larvae, it has been concluded that the promoter is effective because of changes which occur within the organism itself, and not merely in enhancing the spreadability of the oil on the water surface (i.e., acting as a surfactant). A number of other surfactants have been checked, and no other surfactant has been found to give the same effect as the ethoxylated dinonyl phenol. Some of these. other surfactants are ethoxylated nonyl phenols (9 species) and ethoxylated octyl phenols (5 species) with various numbers of ethoxy units in the substituent; ethoxylated amines (2 species); ethoxylated fatty acids (2 species); and 9 other ethoxylated materials.

The present invention can best be understood by a discussion of each of the aspects in sequence. Thus, here,- inbelow will be discussed the specifics of the ethoxylated dinonyl phenol, including the method of preparation and a comparison with other surfactants, the amount of promoter which should be included, the hydrocarbon oils which can be used in connection with the promoter, and the methods of applying the promoted oil for the control of proliferating mosquitoes.

Promoter has the fol- 2,4-dinonyl phenoxy polyethoxy ethanol (referred to herein as polyethoxylated dinonylphenol) In the above formula, x is the number of ethoxy units in the ethoxylated substituent. From 6 to 14 units (average) will be present in the ethoxylated substituent, so that x can be from 6 to 14.

The number of ethoxy units in the ethoxylated substituent is determined by Nuclear Magnetic Resonance (NMR) analysis wherein the amounts of the alkyl, aromatic, ethoxy and hydroxy hydrogens are measured. One third of the aromatic hydrogen measurement should be equal to one thirty-eighth of the alkyl hydrogen measurement. This provides an internal calibration factor (F) for determining the ethoxy chain length. First, the ethoxy hydrogen measurement is divided by the factor F, thereby obtaining the number of ethoxy hydrogens. The number of ethoxy hydrogens divided by 4 gives the average number of ethoxy units in the molecule.

An ethoxylated 2,4-dinonyl phenol is prepared by the liquid phase ethoxylation of 2,4-dinonyl phenol:

I Q-C lln I CsHw In this process, a liquid-phase charge of preferably 85%|- pure dinonyl phenol and up to 0.2% NaOH by weight (based on the amount of dinonyl phenol) is placed in a pressure reactor, and is raised to a temperature of about 260 to 300 F. Gaseous ethylene oxide is bubbled into the reaction zone, wherein an exothermic reaction takes place between the ethylene oxide and the dinonyl phenol. The rate of addition is controlled to maintain a temperature of about 320 to 340 F. From 6 to 14 mols of ethylene oxide per mol of dinonyl phenol are introduced and reacted. The average number of ethoxy units in the ethoxylated substituent can be fairly closely controlled by the ratio of ethylene oxide to dinonyl phenol introduced into the reaction zone.

The reaction is preferably carried out generally at a temperature within the range of 320 to 340 F., and a pressure from atmospheric to p.s.i.g. The ratio of ethylene oxide to phenol is preferably '8 to 11 mols of ethylene oxide per mol of dinonyl phenol. The process is preferably carried out in a semibatch process, with the ethylene oxide being continuously introduced at a controlled rate into a batch reactor. Conditions are preferably controlled so that there is no ethylene oxide in the exhaust gas (i.e., all of the ethylene oxide is reacted). Exemplary products may have the following physical characteristics:

The ethoxylated dinonyl phenol is very effective in promoting the toxic effects of mosquito control oils. This same eifect has not been noted with other surfactants.

In Table 11 below, EODP(8) is compared with exemplary other surface active agents. Note that the use of EODP(8) alone, without an oil, did not produce any appreciable mortality in the test larvae.

TABLE II Percent mortality, Interiacial 24 hrs. exposure larvae tension, Description of material dynes/em. 1. 25* 2. 5* 5. 0*

500600 F. paraffinio oil 50. 0 53 65 EGO-600 F. paraifinic oil with 0.5 wt. percent ethoxylated (5) octyl phenol- 2. 2 36 600-600 F. paratlinie oil with 1875 1 wt. percent EODP (8) 2 -1 45 67 50000 F. paratfinic oil with 0.375

wt. percent EODP (8) 2 1 100 100 500600 F. parafifinic oil with 0.5

wt. percent ethoxylated oleic acid having 10 ethoxy units- 2. 5 36 69 EODP (8) 2 l 0 l Gallons per acre. 2 EODP (8) is ethoxylated 2,4-dinonyl phenol having 8 ethoxy units (average).

Note that the toxic activity of the paraffinic oil was substantially enhanced by employing the promoter of the present invention; whereas the use of ethoxylated (5) octyl phenol (Triton X45, commonly used in 0.25 weight percent combination with diesel fuel for mosquito control) showed no perceptible increase in activity at the low treat rate, nor did the use of ethoxylated (10) oleic acid, although the number of ethoxy units is within the range employed in the present invention.

The purity of the 2,4-dinonyl phenol feedstock into the ethoxylation reaction zone should be at least resulting in a product purity of at least 85%. The main impurity will normally be nonyl phenol, which can itself be ethoxylated to produce a surface active agent which appears to interfere with the activity of the promoter of the present invention. As will be discussed hereinafter, solubilizers such as aromatic hydrocarbons (and especially dinonyl phenol) as well as surface active agents tend to reduce the effectiveness of the promoter, requiring the use of higher concentration of promoter in the oil or a higher oil treat rate, or both. With up to about 10 weight percent impurities in the product, the impurities act primarily as diluents. (The concentration of EODP is always calculated on an impurity-free basis.) Above 15 weight percent, however, deleterious effects are observable and this 15% limit preferably should not be exceeded.

To illustrate the deleterious effect of other surface active agents (particularly, the ethoxylated nonyl phenol, mortality studies were made with a 500600 F. parafiinic oil containing 1 weight percent EODP (8.7), and companion runs to which were added one or two additional 0.25 weight percent increments of EONP (8).

1 EODP (8.7) is ethoxylated 2,4-dinonyl phenol containing an average of 8.7 ethoxy units per molecule.

2 EONP (8) is ethoxylated nonyl phenol containing an average of 8 ethoxy units per molecule.

Note that the addition of ethoxylated nonyl phenol reduced the effectiveness of the promoter from 99% to 84% to 41%. This is not a dilution effect since the amount of EODP (8.7) is not reduced. Thus, high purity dinonyl phenol is to be preferred.

The promoter of the present invention can be utilized in varying concentrations. As has been seen from Table 3,499,969 6 IV below, the use of at least 0.1875 weight percent is and therefore the range of 8 to 11 units (possibly higher) required before any eifect is seen. is preferred. Note that even at 5.6 units per molecule,

TABLE IV RELATION OF TOXICITY OF AN WITH the toxicity to pupae is enhanced so that essentially the ETHYLOXYLATED DINONYL PHENOL AT VARIOU same effectiveness is obtained at 1.25 gallons per acre CONCENTRATION LEVELS 5 as is accomplished by an oil promoted with 2,4-dinony1 phenol and applied at twice that rate (2.5 gal/acre). Also note that at 14 units per molecule, the larvae toxicity Percent mortality, 24-hr. exposure Larvae Pupae Concentration Interfagial is beginning to decrease rapidly.

of EODP, tension, 1.25 2.5 1.25 2.5

wt. percent dynes/cm. (gal/a.) (gaL/a.) (gaL/a.) (gaL/a.) 1O Su table 011 50 55 4 5s -1 21 e5 64 87 The promoter of the present mvention may be used 3 8 3; with a number of hydrocarbon oils which themselves -1 100 100 100 96 have toxicity for the aquatic stages of mosquito life. In :3 15 general, these oils will boil within the range of 500 to 0 I 800 F., and may include parafiinic oils, alkylate oils, 500-600 F-Parafinm diesel fuel, and C to C paraflins, preferably having a As the treat rate decreases, the required concentration midpoint below 650 F. The preferred boiling range is at which the effectiveness increases sharply has been from 500 to 725 F., and the preferred oil will be in the found t0 be higher an that required at higher treat 20 higher regions in this range, e.g., 550-650 F. Asuitable, rates. For example, at 1.0 gallon per acre treat rate, the economically available oil, however, may be a paraffinic oil of Table IV should contain 0.75 weight percent EODP oil boiling from 500 to 600 F. A midpoint of 650 F if a 24-hour mortality rate higher than 90% is desired. or less is preferred (Table VII).

Preferably, about 0.375 weight percent is employed in Examples of suitable oils are shown below, with an the mixture, since at this point the spread rate of one 25 example of ea h type being given along with the ins eegallon per acre shows essentia ly a 100% morta i y n tion data. An aromatic oil is shown for comparison, .to both larvae and P P It is belifived that a concentration illustrate the deleterious effect of aromatics. Other aro- 0f 10% Would represent an pp economic limit, matic oils which have been evaluated show similar realthough the use of higher concentrations (e.g., 3.75 l s T b1 V111, f l

weight percent) is technically feasible although prohibin tively costly. The presence of aromatic hydrocarbons, TABLE VI solubilizers such as nonyl phenol, and other surfactants Amount f Wlll require the use of greater than normal amounts of A EODP. dinonyl Percent mortality 24-hr. exposure Ethoxylated 2,4-d1nonyl phenol 1s very effective in re- 1 25 323 Larvae P as ducing interfacial tension. As seen in FIG. 1, 0.03 weight up percent reduces the interfacial tension to about 2 dynes/ Suitable Oils p cent 1. 25 2.5 5.0 1.25 2.5 1 5.0 cm. From 0 to 0.03 weight percent concentration provides paragnic 011 None 53 65 56 64 the most striking reduction in interfacial tension, and Pam 1110 Oil 1375 100 92 93 98 1k 1 i1 3 the spreadibility of the hydrocarbon 011 would be most 3 5 3: E f 5%;; 100 38 88 substantially benefitted in this range. As has been seen 131656101916 None 11 19 32 33 97 D 1 375 2 in Table IV, however, use of 0.1875 weight percent i5i %f, 0 97 100 9 99 100 (7) None 71 100 93 ethoxylated (8 2,4 drnonyl phenol (preferably about N C16 Paramm 0375 92 100 m0 100 0.375) is required before a substantial effect 18 seen on Aromatic None 67 33 the larvae. This concentration is substantially above the Aromatic 0'375 28 59 21 level of 0.03 weight percent which is seen to substantially modify interfacial tension and illustrates that this invention is not merely related to spreadability of the hydro- Inspectwn data (011) carbon on the water surface. However, in view of the Inspection 1 a 5 7 9 deleter ous effects of othensurfactants, solubllizers, and Midbofling pHF 572 542 515 585 aromatic hydrocarbons, 1t 1s believed that the presence s gs-s y b nin r rn f lfi u 120 160 and artztivtity of the promoter at the oil/water 1nterface 1s iiji gffz 2 2 252i 2 impor an 5 5 09 e The amount of the promoted oil mixture which is used 2, ,2 8

can also be a function of the number of ethoxy groups 55 in the ethoxylated substituent. This can be seen in Table 93 ,gg V below which compares the effectiveness at 0.5 weight I ArI 1-nvit 31.5 41.2 percent concentrations of 2,4-dinonyl phenols having VSCOSIW SSU at 100 F 50 different average numbers of ethoxy units in the ethox- :Gallons per acre. ylated substituent. 0 Welght TABLE V Percent mortality, 24-hr. exposure, gaL/acre Average number of Larvae Pupae ethoxy units on 2, 4- dinonyl phenol l. 0 1. 25 1. 5 2. 5 5. 0 1. 25 2. 5 5. 0

Norm-Promoter is used in 0.5 weight percent concentration in a SOD-600 F. parathnic oil.

From Table V it is seen that at 5.6 units (average) Note that the promoter of the present invention is efper molecule, a certain amount of effectiveness is profective on a wide range of 01]. types and 1s particularly vided. However, at an average of 8 and 11 units per effective in enhancing the toxicity of paraffinic oils. The molecule, a much greater effect on the larvae is seen, higher boiling oils are not desirable since some of them do not possess the requisite toxicity. Thus, the midpoint should be less than 650 F. as shown below in Table VII.

TABLE VII per acre; although in some circumstances, it may be economic to apply even greater quantities.

Unsulfonated CuleI fatigmts, Larvae percent mortality residue,

Midpoint percent F.

SSU 100 F.

1.0 (gal/a.) 1.25 (gal./a.)

1.5 (gaL/a.) 2.5 (gaL/a.)

1 Same as oil (1) in Table VI.

2 Oil (1) with low 20% cut removed.

3 Oil (1) with low 40% cut removed.

4 Same as oil (3) in Table VI.

6 E, F and G are higher-boiling cuts of an oil similar to oil (3).

H, I, J, K and L are 50-70 vis lube stocks. All oils contained 1 wt. percent EODP (8) except D, which contained TABLE VIII.24-Hr. Mortality, C. fatigans Larvae, Oil Containing 1 Wt. Percent EODP (8) HAN l Aromatic G aL/acre IIexadeeane vol. content,

v01. percent percent vol. percent 0. 75 1. 0 l. 25 1.

l HAN is a heavy aromatic naphtha boiling from 360 to 530 F. with a 20.1 .API gravity and a 90% aromatic content. Ilexadecane boils at 548 F.

Note from Table VIII that an increasing aromatic content decreased the effectiveness of the promoted oil. It is believed that this is due to the solubilizing effect of the aromatic hydrocarbons, which disturbs in some way not known the activity of the EODP at the oil-water interface. From Table VIII it appears that the oil should contain at least 60% saturated hydrocarbon at higher treat rates, and at least 80% for treat rates of about 1.0 gal./acre, if 90%+ mortality is desired.

The mixture of oil and promoter can be applied to the surface of breeding ponds in a number of different ways. It can obviously be poured as a liquid mixture directly onto the surface of the ponds or can be sprayed on the surface of the ponds by devices carried by hand, mounted on trucks, or carried by aerial applicators such as airplanes and helicopters. Submerged tanks may be employed which discharge the oil slowly for maintaining an effective oil layer on the surface. In many cases, the equipment available for applying the oil to the surface of the ponds is not capable of metering out the small quantities at which the present mixture is effective. Although not economically attractive, it is possible to use diluent oils (such as kerosene) to provide bulk for application. The promoted oil should be applied at a rate of at least one gallon per acre, preferably within the range from 1 to 3 gallons of the promoted oil mixture per acre (for the purpose of determining the application rate, where a diluted oil mixture is applied, the diluent oil is not counted as part of the oil being applied to the 'water surface). The upper limit of the application rate is based upon economics and would be probably about 10 gallons 0.5 wt. percent.

As is seen below in the table, the volatility of the oil influences the effectiveness of the mixture.

TAB LE IX.Residual Toxicity to C. fatigans Larvae IBP Percent mortality, 5 gal/a. dosage Material CF.) 0 1 2 3 4 5 G 7 A. Paraillnie oil with 0.5

wt. percent EODP (8)...- 500 100 100 83 68 33 28 0 B. Diesel fuel with 0.5 wt.

percent EODP (8).... 400 100 100 8 C. Diesel fuel... 400 20 1 1 Age of the film in days before addition of test animals.

Table IX shows that, as the volatile components of the oil are lost with time, the effectiveness is decreased. Thus, the use of higher boiling oil fractions (that are toxic in themselves) are preferred for more effective control. New eggs hatch in 2 to 3 days, thus the lasting effectiveness of the oil is beneficial.

The data tabulated above was obtained by the following experimental procedure. Beakers (400 ml. capacity and 7.4 cm. internal diameter) containing 250 ml. of distilled water were used for all tests. The test animals were laboratory specimens of C. fatigans selected at random from pools of larvae or pupae representing combined rearing pans. Twenty-five fourth instar larvae or pupae were used per beaker. Untreated and diesel oil controls were included in each test.

To test toxicity, the larvae (or pupae) were placed in each beaker, following which 0.005 ml., 0.01 ml. or 0.02 ml. of oil was dropped on the water surface with a pipette. These quantities represent a rate of 1.25 gal/acre, 2.5 gal./ acre and 5.0 gal/acre, respectively. Twenty-four hours later the number of living and dead specimens was recorded and the percent mortality determined. This test was conducted in triplicate, with 25 specimens being used per replicate.

To establish the residual effectiveness of the promoted oils, the following tests were made. The oils were pipetted onto the surface of water in beakers at the rate of 5 gallons per acre and C. fatigans larvae were introduced into the separate beakers at various times up to 7 days after the oil was deposited on the water surface, and the 24- hour toxicity was observed.

I claim:

1. A mosquito control oil consisting essentially of (a) a hydrocarbon oil boiling substantially within the range from 500 F. to 800 F. and having a midpoint no greater than 650 F., containing at least 60% saturated hydrocarbons, and having a toxicity toward immature mosquitoes, and

(b) from about 0.2 weight percent to about 3.75

weight percent concentration of polyethoxylated 2,4- dinoyl phenol which contains an average of from about 6 to about 14 ethoxy units in the ethoxylated substituent.

2. A mosquito control oil in accordance with claim 1 wherein the hydrocarbon oil contains at least 80% saturated hydrocarbons.

3. A mosquito control oil in accordance with claim 1 wherein the polyethoxylated 2,4-dinonyl phenol is presentin a concentration from about 0.2 weight percent to about 1.0 weight percent.

4. A mosquito control oil in accordance with claim 1 wherein the polyethoxylated 2,4-dinonyl phenol is present in a concentration of about 0.75 weight percent.

5. A mosquito control oil in accordance with claim 1 wherein the hydrocarbon oil contains at least 90% saturated hydrocarbons.

6. A mosquito control oil in accordance with claim 1 wherein the hydrocarbon oil boils substantially within the range from about 500 F. to about 600 F.

7. A mosquito control oil in accordance with. claim 6 wherein the hydrocarbon oil contains at least 80% saturated hydrocarbons.

8. A mosquito control oil in accordance with claim 6 wherein the hydrocarbon oil contains at least 90% saturated hydrocarbons.

9. A mosquito control oil in accordance with claim 1 wherein the hydrocarbon oil boils substantially within the range from about 550 F. to about 650 F.

10. A mosquito control oil in accordance with claim 9 wherein the hydrocarbon oil contains at least 80% saturated hydrocarbons.

11. A mosquito control in accordance with claim 9 wherein the hydrocarbon oil contains at least 90% saturated hydrocarbons.

1 2. A mosquito control oil in accordance with claim 9 wherein the polyethoxylated 2,4-dinonyl phenol contains from 8 to 11 ethoxy units.

13. A mosquito control oil in accordance with claim 1 wherein the polyethoxylated 2,4-dinonyl phenol contains from 8 to 11 ethoxylated units.

14. A mosquito control oil in accordance with claim 13 wherein the polyethoxylated 2,4-dinonyl phenol is present in a concentration from about 0.2 weight percent to about 1.0 weight percent.

15. A mosquito control oil in accordance with claim 13 wherein the polyethoxylated 2.,4-dinonyl phenol is present in a concentration of about 0.75 weight percent.

16. A mosquito control oil in accordance with claim 1 wherein the polyethoxylated 2,4-dinonyl phenol contains about 8 ethoxy units.

17. A mosquito control oil in accordance with claim 16 wherein the polyethoxylated 2,4-dinonyl phenol is present in a concentration from about 0.2 weight percent to about 1.0 Weight percent.

18. A mosquito control oil in accordance with claim 16 wherein the polyethoxylated 2,4-dinonyl phenol is present in a concentration from about 0.75 weight percent.

19. A mosquito control oil in accordance with claim 1 wherein the hydrocarbon oil boils substantially within the range from about 500 F. to about 600 F. and the polyethoxylated 2,4-dinonyl phenol is present in a concentration of about 0.75 weight percent.

20. A mosquito control oil in accordance with claim 19 wherein the polyethoxylated 2,4-dinonyl phenol contains about 8 ethoxy units.

21. A mosquito control oil in accordance with claim 20 wherein the hydrocarbon oil has the following characteristics:

Viscosity50 SSU at 100 F. Aromatic content-12 volume percent API gravity-31.5

ASTM D-86-IBP508 F.

22. A method of killing immature mosquitoes which comprises applying to the surface of a mosquito breeding pond at a rate of at least 0.5 gallon per acre of exposed pond surface a mosquito control oil consisting essentially of:

(a) a hydrocarbon oil boiling substantially within the range from 500 F. to 800 F. and having a midpoint no greater than 650 F., containing at least 60% saturated hydrocarbons, and having a toxicity toward immature mosquitoes, and (b) from about 0.2 weight percent to about 3.75 weight percent concentration of polyethoxylated 2,4-dinonyl phenol which contains an average of from about 6 to about 14 ethoxy units in the ethoxylated substituent.

23. A method according to claim 22 wherein the oil is a paraffinic oil having a boiling range from about 500 F. to about 600 F., a viscosity of about 50 SSU at F. and an aromatic content of about 12 volume percent, and an API gravity of about 31.5.

24. A method in accordance with claim 23 wherein the application rate is from about 0.5 gallon to about 2.5 gallons per acre.

25. A method in accordance with claim 23 wherein the polyethoxylated 2,4-dinonyl phenol contains about 8 ethoxy units and is present in a concentration of about 0.75 weight percent.

References Cited UNITED STATES PATENTS 1/1938 Coleman et al. 196149 8/1963 Mansfield 260--613 OTHER REFERENCES FRANK CACCIAPAGLIA, JR., Primary Examiner I. V. COSTIGAN, Assistant Examiner U.S. Cl. X.R. 424355, 356 

